The present invention generally relates to a lighting instrument for use in microsurgical procedures, in particular for use in ophthamologic microsurgery in the hyaloid or vitreous humor of the eye, and more particularly relates to a lighting instrument of a type including an optic light guide traversing a cannula or hollow needle and connected to a light source for insertion in a vessel or chamber of the vitreous humor of the eye.
In vitreous surgery, the use of ophthalmologic illuminating probes in form of optic light guides is proposed which are so designed at their tip as to enlarge the radiating light cone. Such light guides, or light guides that are further enhanced by being outfitted at their tip with a microscopic device or lens, provide oftentimes insufficient illumination of the chamber in the vitreous humor to allow a clear diagnosis or to perform a surgical procedure. Moreover, conventional light guides are incapable to provide sufficient illumination in the vitreous humor of the eye near the point of entry of the light probe into the eye. Conventional light probes provide also insufficient lighting of the retina especially in cases where the lighting has to be sufficiently extensive to provide lighting behind some bumps which can occur on the retina and which sometimes obstruct the light path. This situation occurs most frequently when the point of entry of the light guide is situated in the same quadrant of the vitreous humor as the region to be illuminated. Also, conventional light guides encounter the drawback that light rays are reflected in such a way that the surgeon or diagnostician is blinded by improperly reflected light rays, thus leading to imprecision and complications of the surgical procedures.
European Pat. No. EP-A 0 651 981 discloses a lighting probe for vitreous surgery, which is particularly adapted to enlarge the spatial angle of light radiating from the light guide, by constructing the tip of the light guide of frustoconical shape and with tapering exit area. Alternatively, the light guide is formed as a truncated cylinder which has one end face provided with a micro-optical element or lens.
Other conventional microsurgical instruments for illuminating a surgical site in a vessel or vitreous humor are disclosed e.g. in U.S. Pat. Nos. 4,733,937 and 4,551,129, which describe light guides that are formed at their ends where light exits with additional optical devices in the form of lenses or the like.